Dental drill



Feb. 25, 1958 R. PAGE H ,DENTAL DRILL I 3 Sheets- Sheet 1 Fild Sept. 15,1955 lNVEjNTOR 1 RICHARD W. PAGE.

I NEY DENTAIJDRILL RichardW. Page,: Chappaqua,., N. Y.,,assignor to,Cliityes Dental; InstrumentQCo'rporatidn, New York, N. 'Y., a:corporation of New York Application September .13, 1955,tSe'rial-lIo'.--53,4;03'I- 4 (Cl'."32-i27) 1 This invention relates'to dentaldrills and; morezparticu irt larly y to high speed dentai drilliiigequiprnent. r

' United States Patent CdnventionaF-dental drillingequipmentilasuheretofore:

used utilizes a comparatively slowly rotating drill5(about1 16,00O R. PEM1 being fairly typical); the drive tottthe hand pie'cesbeingggenerally::asbeltxandnpulley .driveizandi the internaldrive connection:to theadrill::proper:.bein a;

gear connecti'on. The speed possibilitiesxof a =drive 4 this" character:arequite limited-s Withrth'esadvent ofleare bid'e and diamonddrillsuand:with the development :05; air and waterssystems-*forsusevwithsuchedrillsgtheadesiran bility':ofa-greally high speedzdental drillhaszzbeencapparrz enciforisome ayears:1: t

The general object: ioft ithwpresent:inventionsis:ztozproei vide em:improvedxldental :drillingninstrumentncapahletvofit operation: at.extremelyzahighrspeedsz,

Aisecond-tobjectzofiIheeiriventiomisito providetan'i:im.

provedxdrillin'g sheath arrangement: which sziS :wcapablei f--furnishingunaximum: protection .to rotative bearing'sielee mentsragainst: the 1 entry; ofri water; ',dlillingl ide,tl'itnsliamit otherpossible injurious: substaneesta A 7 further :robject :is to :provide :a.identail drillingr ins r5 mentvcapablenof operatingrwitharan minimumsofaseniittivity. Ofl vibration ;on:1he zpart: of the; patient; t

stillrenothentrobject ofizthe invention is; tQmP oMidee-at dentabdrilling: instrument ;operable,-.with1a minimum :10:-

pressure ofithezcutting.:tool againstra; tooth,- resnlti grin;..

2,824,370 Patented F eh. 2 5, 1958 2;" fixediinvsthe. casing element-2;.carries a;shaft:;5,-;.the,..tip oft which-iistheld in .tamsupportingmembers 6 :attached tO-dhea engine-:arm. Rotatablymounted;on-z-the,::shaft:; assemblyazincluding-v';at pulley: 7;,driven;:by beltr a v enginezarm and pulley 9rotatablettherewithr;andtwhich; driyescthe :vdrill'" as hereinafterdescribed; ingdetail.

The :details' ofcthe engine :arrn: end iof; th.e; contra-angle;isishownmore fully; in:;Figs.;e5 and Zfii Asivthereashown; shaft;.5 .hasa groove :10 1 adjacent its; tip which, ;cooperat.es; withazspringspressed- 'detent. ball 11' ,ionreleasahly gholda ingthe-shaftr5 inz-the engine arm element 6.; The engine arm,drivempulleyfl is coup1ed:to theielement ,6;by means," of a snap gring-12; received in a groove v13 :inthe; element 6, and- -hasan internallythreaded hub;;14. which: screws onto externallyythreaded hub portion/:15rzOf :the pulley 9.1- Spring fingers 16;engaging a,tweb of the pulley ;9further 'serve .-;to couple-the .parts together: The hub 1' of: pulley 9is alsofqrmed-mith-a bore 17 withinwhichtare located antisfrietion ballbearings?18,- separated by a collar 1-19 awhichsrnay be ifiXed inposition ,on ,theshaft 5 by;-me.ans. of,a.sett-screwazmaccess to whichis-furnished through holes 21in ,the hubs, A- retainerring 22 fitting inaigroove 23 serves--to hold,thetbearings ,;18'and-collar 19 .in. saxial.position ,iwithinnthewhub :of pulley '9. The pulleys); ipreterablyahasralargeridiameteratthan, pulleyj, at ratio of. about; 271- as; shown; beinsatisfactory ;and providing a step up in belt speed.

I The-drive within-Abe:contrarangletitself isa-beh drive and! comprisesidletpulleys ,30 and 3L and a drivenrpulley 32,.arrangedlas shown. Thedrivenspulley-32 ish-concen-r trier with nthfl .rdrill'lfcarrying socket:or element 33,5 and v theyidle tpulleys 3l areflarranged vto.-:maintain.,thei.be1t

courses between pulleys :31 and ..pu1ley. 32 :at right angles to theaxis ofithesdrillrsocket.,33,tsorasv.tomaintaintthe belt-courses(Fig-l, 1) The .spacing; of .pulleys- 131 from each.oth.er,t(Fig. 2):may be such as..to.;gu ide,the b'elt courses C lq ingsubstantialhparallelism, a providing 180 of jwrap ofthepbelt-on ,the driven pulleyiil, Pulleys 30;arev locatedtsor as :to maintain rthezbelt'coursesclbetween them andlipulleys 31 in parallelism and ,t0. maintainthe courses C 3;between, pulleys;,30 vandltthe v drive pulley 9" in aplane .at ri ht angles 7toshaft 5 and with the .courses C 3 and 'C-2"defining.planes ,at. rigl 1't angles to the axes of, rotation of thepulleys 30." It will be observed that the pulleys 30are toed in so as togive an angle of wrap of 'the'b'elt'on pulley 9"which"isma- I teriallyin-excessjof ,180"; The diameter [of pulley 9 is also relativelylargeiby comparison with that iof-rpulley -32,- soas -to'--obtain astepupin rotative speed? The *ra tio maybe *5 or 6 to '1. For example,driven pulley 32' has -=in onc actual instrument; a diameter-of -.165inch;

Fig= 4 is anenlarged detail, of a part-oftFig 7, showing;

arseal adjacent the :drill bearing;

Fig,;5 is. an enlarged section on :line =-5-.-5 'ofaFig;;;,2;v, Fig-e6is-tan. -exp ioded view, vshowing the parts ofizEig 5.separatedrfromueach other; 7

Fig.7 is an enlarged section on theiline. 77 .0v.Fig. 2;. Fig 8 is:. a.-sideelevational view, .with.;parts'.- broken. away, of. at modified term"of .drillin'g instrument; ,7

Figg 9 is an endfele'vation of "the instrument of'jFifiQSj Figs, 10 andlliare, respectively, a top...p laniview andx The belt 'need not bemassive and a belt-a 'inch' P in, widtheand 1?? .024 in thickness hasb'een 1 found satisfac tory, the over-all length being about 18' inches.

Any-tof a variety of 'plastic or rubber materialsor combinations of suchsmaterialswith' -textile fibers rnaybe used; and coefficient of frictionof belt and metal having a-normal: value of 'a-bout 1.25 has *beenf'oundsatisfactory.

0 i Arthe rdrilliend of. theinstrument, the dr 'ill socket 33 3 is-aeetiimilar-t Fig 7, b h in 5 be heldain place-by a pin 45;: Endtcapjgelements46,q47

servertortholclw theparts:,in: position;- axiallyqof thee drill g, 4a il e v e h i m a t qio 5 sockets33. The bearing housing 48; is formed{integral part nfi Fig: 131

The-instrument :o'f: Figse; 1+7 is: a: contra-tangle: adapted wit-h};or,:fixed,-to the casing section- 1,, as .indicated, and hasan-aaccuratercylindrical inner; surface or] bore .49 ,with-j Ittcomprisestaacasing;includin lescopednelements 1.. andszt; adjustably'zheldttogethertb.aiscrewfia Bloc,

Thelements :42431'? ofrannularrform, ,and extend. com:

pletely around the pulley and bearings, whiielthetel the same as betweenthe pulley and ring 42). Asthere.

shown, the pulley flange 51 is recessed on its outer face 52 and theinner part 53 of ring 43 fits this recess, having a slight operatingclearance from the pulley flange 51 and also from the adjacent innerrace of the ball bearing .41. An air connection 55 (Fig. 7) is providedand air is continuously supplied through this element so as to maintaintheinner part of the casing 49 under slight pressure and also to exhaustair at point 56 between the drill socket 33 and element 47, was toinsure that dirt, tooth particles and the like will not get into thebearings. The drill chuck comprises a rubber sleeve 57 into which theshank 58 of the drill is frictionally fitted.

The drive of pulley 7 and belt 8 may be conventional and presents nospecial problems, speeds from 15,000- 30,000 R. P. M. at this pointbeing readily obtainable and producing idle rotation speeds of the drillfrom 60,000 to 100,000 R. P. M. or even higher.

The belt tension may be readily adjusted by varying the degree oftelescoping of easing sections 1 and 2 and then fastening in theadjusted position by means of the screw 3. A tension somewhat less than8 ounces and typically about 3 or 4 ounces (total static tension) isfound suitable. When running, the belt appears to run It is found thatthe instrument of the invention operates most satisfactorily withcarboloy or similar cutters formed with definite cutting edges, asopposed to abrasive tools, and the action obtained appears to be a truechiseling cutting or flaking action, as opposed to a grinding action.Using a burr having six cutting edges, the theoretical number of cutsmay be S or thousand per second, which is divided into, the quantity ofenamel removed per second in cavity preparation, the result inproduction of particles of an average size corresponding to animpalpable dust or colloidal material. It is found, however, that thechip size is not small and the surface on which the drill has beenoperating presents the chartaut on one side and slack on the other, sothat tension 1 in the driven or taut side of the belt is presumablyabout 3 or 4 ounces.

The desired belt tension may be readily provided by holding theinstrument with the end uppermost and drill lowermost, and hanging afixed weight from the drill, the lock screw 3 being backed off orloosened. Under these conditions, the weight is suspended by thetensions on the belt and the belt tension may be fixed by tightening thescrew 3 and then removing the weight.

The drive of the presentinvention is of a surprisingly eflicientcharacter in view of the speeds involved and in view of the size limitsof certain of the parts. For example, with the drive pulley 9 running atabout 14,000 R. P. M. idling speed, the belt speed is around 300 feetper minute, while the angle of bend around the driven pulley is quitesharp, it is found that the wear on the belt is negligible, and to apoint where the belt may be expected to outlast the bearings. Theservice life of the bearings themselves has been found to be comparableto conventional slow speed gear driven units. I

Stroboscopic speed measurements have indicated percentage of slip on thebelt and the driven pulley 32, when idling, of about 10%, the drivenpulley running at about 72,000 R. P. M. as compared to something over80,000 R. P. M. theoretical no slip speed of rota tion. Under drillingconditions, the slip occurs, the slip percentage rising to, perhaps,25%, and ,sufiicient torque being exerted in some cases so as to cause aslowing down of the pulley 9.

The instrument has been operated to advantage with drive pulley speedsfrom 14,000 to 30,000 R. P. M., cor-, responding to indicated drillrotative speeds from 81,000 to 160,000 R. P. M. and over, and the actualdrill ro' tative speeds considering slippage from 50,000 to 100,000 R.P. M. and over.

The instrument appears to be capable, of delivering the major portion ofthe rated horse power of the engine arm motor at the drill tip, as thecoefiicient of fricacteristic appearance of a machine milled surface,indicating the cutting and flaking action, as opposed to abrasiveaction. The time involved in cavity preparation is very materiallyreduced and the discomfort to the patient is also substantially reduced.Vibration does not appear to be a problem, and, in fact, some patientswhere novocaine was used have professed inability to tell whether thetooth waslbeing drilled or not.

Figs. 8-13 illustrate a somewhat modified form of instrument. In. thisinstrument corresponding parts are identified by numerals similar tothose used in previous figures, but with the addition of the letter a,the applicable description does not require repetition and will not berepeated. In this modified instrument, there are shown air and watersupply nozzles and 61, as well as an air supply line 62 for the drillbearing housing. In order to prevent operation of the instrument when noair is being supplied through line 62, line 62 has a branch (Fig. 12)leading to a bladder or bellows 63, which engages the head 64 of a lockpin 65, arranged to enter the recess 66 in the drive pulley 9a. A spring67 normally urges the pin into the recess 66, preventing rotation of thedrill. If, however, air under the desired pressure is being suppliedthrough the line 62, the resulting expansion of element 63 will hold thepin back in the position of Fig. 12 and out of the recess 66, includingelement 9a, thus permitting operation of the device. This insures thatthe instrument will not be operated without air pressure in the drillbearing housing 480 and thus protects the drill against use underconditions where water and detritus might enter the bearings due tooversight on the part of the dentist in failing to turn on the air. Inthis modification, the drill shank 58b is received ina. rubber or otherresilient sleeve 57a, as before, but this sleeve is bonded to the insideof the tubular shell or'socket 70, which, in turn, fits in the socket33a and is secured therein by'threaded sections on the two elementsengaging at 71, as shown.

The resilient mounting ofthe drill shank in the device I of the presentinvention permits a slight lateral movement I the drill tip, whenidling, rotates eccentrically, the axis tion between belt and pulleymultiplied by the linear tial percentage of idle speed will increase theslip to such an extent as IQ CaUSC a relatively high torque and powerconsumption. I 1

moving in a cone, the diameter of which at the burr is a substantialfraction of the entire width of the burr and may, in extreme, cases,equal the width of the burr tip itself. The drill is used with extremelylight pressure, requiringasomewhat different technique from regulardrilling equipment, but a technique which is readily acquired, thedrilling pressure being of the order of a quar: ter of an ounce or so,or about 10 grams, which pres- ;ure is far belowanything previouslyused. Whereas with conventional drilling equipment an increase indrilling pressure tends to produce a proportional or even greaterincrease in rate of removal of material at a given operating speed, theinstrument of the present invention appears to'have a cutting speed atgiven rotary speed, which is substantially determined and does not varywith I, a variation in applied pressure, the effect of an attempt toincrease pressure being to diminish the rate of removal of materialrather than to increase it. I

The eccentric drill appears to operate by making approximately one cutfor each revolution, so that a drill operating at 120,000 R. P. M. makesabout 2,000 cuts per second, and a drill operating at 60,000 R. P. M.makes about 1,000 cuts per second, as opposed to 12,000-6,000 cuts persecond, which would be the case if each successive tooth or cutting edgein a six toothed burr were effective. It will be noted that due to theextremely high rotary speed of the drill, even these frequencies of1,000 or 2,000 cuts per second are well above the vibration frequencieswhich cause maximum unpleasantness to practically all patients, whichfrequencies tend to be around 200 cycles per second and would seldomexceed 600 cycles per second (Hudson et al., Journal of the AmericanDental Association, volume 50, page 378), and also above the upperthreshold of perception to vibration for almost all patients (ibid). Ithas thus been found possible to operate with an eccentrically rotatingdrill without objectionable vibration and with a very marked improvementin cutting action.

The device is operated using water spray and preferably, air and watermist spray as a coolant and no difficulty due to heating of the toothWhile drilling is experienced. While used in the manner stated in thedrilling of enamel or hard material, the drill may also be operated atreduced speeds of a few thousand R. P. M. for the drilling of carious orother soft material. In this case, the centrifugal eifect in causingeccentric rotation 5 of the drill becomes negligible, the operation isessentially conventional and the successive cutting edges of the tip areoperated in order as in the usual drill.

While it has never previously been thought or found possible to operatean angle dental drilling instrument by means of a pulley drive, nodifliculty is exeperienced in the device of the present invention, sincethe operation involves essentially two distnict and entirely differentdrilling conditions, the instrument performing satisfactorily underthese two different conditions but for entirely different reasons. Inthe drilling of soft material, the power required is low and it ispossible to operate at slow speeds as just mentioned, even though thetorque transmitting capacity of the drive is very small. In the drillingof hard material at high speeds, however, the torque required totransmit the necessary power becomes again very small, so that it ispossible to deliver the required power even though using a driven pulleyof such small size as is necessary to fit within an operating head ofconventional and practical size.

The deivce has little or no tendency to stall when operated properly.Essentially, the drive is, as mentioned above, a slipping drive, inwhich the torque is proportional to the slipping speed or difference inlinear rate of travel between the belt and the driven pulley on whichthe drill chuck is carried. Assuming an approximately constantcoefficient of friction, and constant speed of rotation in the drivingpulley and the engine arm of the instrument, it will be observed that anincrease in percentage of slip from about to about as between idling andworking conditions, involves 250% increase in torque, while a reductionin speed involved under these conditions is only about 20% or less. Theresult, of course, under the assumed conditions, is an increase of powertransmitted from belt to the driven pulley of about 200%.

A division of power as between friction losses in the bearings and thepower consumed in drilling being in some such ratio as l-3. It will beapparent that by the use of a very simple driving mechanism involving apulley driven bya belt operating at a very reasonable linear rate oftravel, a drive having the desirable characteristics of a fluid driveand none of the defects of a gear or similar drive has been providedand, moreover, a drive capable within the space requirements of a dentaldrilling instrument of providing speeds far in excess of anythingheretofore obtained.

What is claimed is:

1. A dental drilling angle instrument comprising an elongated rigidframe structure, a chuck for holding a drill, bearings rotatablysupporting the chuck in the frame structure at an angle to thelongitudinal axis of the frame structure, a pulley carried by the chuckfor driving the chuck, a pulley drive for said pulley, including alarger diameter drive pulley carried by the said frame structure, meansfor driving the drive pulley from a dental engine arm, the said drivepulley being mounted for rotation about an axis substantially parallelto the longitudinal axis of the elongated frame structure, and idleguide pulleys carried by the said frame structure and arranged withrelation to the driving pulley and driven pulley for guiding the beltgenerally parallel to the longitudinal axis of the frame structure.

2. A dental drilling angle instrument according to claim 1, in which thesaid bearings are of greater diameter than the driven pulley pitchdiameter, the driven pulley has an overall diameter of only aboutone-quarter inch and comprising a casing enclosing the bearings anddriven pulley, which casing has an over-all diameter of approximatelythree-eighths inch.

3. A dental drilling angle instrument comprising a chuck for holding adrill, bearings rotatably supporting the chuck, a pulley for driving thechuck, a pulley drive for said pulley, including a larger diameter drivepulley, means for driving the drive pulley from a dental engine arm, thesaid drive pulley being mounted for rotation about an axis substantiallyparallel to the axis of the instrument, and idle guide pulleys carriedby the instrument comprising a pair of guide pulleys adjacent the drivepulley, and toed in with respect to each other to give something morethan of wrap of the belt on the said drive pulley.

4. A dental drilling instrument according to claim 3, having alsofurther idle guide pulleys intermediate the first two said guide pulleysand the driven pulley, the said idle pulleys being positioned withrelation to each other and to the driving pulley for maintaining thebelt courses as they approach and leave a guide pulley adjacent thedriving or driven pulley in planes tangent to the pitch lines of thedriving pulley and driven pulleys respectively.

References Cited in the file of this patent UNITED STATES PATENTS2,078,859 Lapham Apr. 27, 1937 2,442,033 Brantly et a1. May 25, 19482,611,960 Herndon Sept. 30, 1952 FOREIGN PATENTS 437,446 France Feb. 17,1912 515,349 Great Britain Dec. 4, 1937

